I remember of a friend who gave up his studies and went all-in on AMP coin (Synereo - if you remember the project). By saying all-in, I don't mean that he invested any money on it but all his time. He worked as a programmer for them and used to earn $300 worth of AMP each month. He did this for at least 3 years, the project did well and he almost became a double millionaire when the spike occurred in markets during 2017 when BTC was $14k and reached $20k. But he kept the coins as it is, didn't sell them when I even advised him to do so and later when the crash happened, the project itself came to an end putting all his work and savings under the grave. So, you need to know when to sell as that's too an important part of trading.
Same here with the DeepOnion shitcoin. Got free airdrop worth of 18K USD when BTC was at ATH back in 2017. Didn't sell a single coin cuz of greed and also I was a complete noob in all this trading stuff. Decided to HODL and now the coin is completely dead. However, I kept checking out the project from time to time and earlier this year I saw that they're getting delisted from many exchanges so I said to myself: "That's it, I'm withdrawing everything" and I managed to withdraw $700 which I put into BTC, made it to $2500 with trading and now I sold everything when BTC was at 19,2K USD. Valuable lesson learned 